Projected Climate Change Effects on Cisco, a Keystone Whitefish Species in Deep Wisconsin Lakes
John Lyons
WDNR Fish and Aquatic Research, Madison
Why Do Cisco Matter?
Adult Gamefish (e.g., musky, walleye)
Climate Change Indicator
Fishery
(spawning, winter)
Zooplankton
Juvenile Gamefish (e.g., musky, walleye)
Water Clarity
(algae conditions)
Where Do Cisco Live in Wisconsin?
Deep (> 50 ft) Lakes!
Examples:
Lake Michigan
Lake Geneva
Okauchee Lake
Lake Mendota
Big Green Lake
Chain of Lakes
Long Lake (Chippewa Co.)
Long Lake (Washburn Co.)
Lake Owen
Turtle‐Flambeau Flowage
Lake Tomahawk
Trout Lake
Lake Superior
Found in ~175 Lakes
Cold Water
Prefer: 40‐65 o F
Stressful: 65‐75 o F
Lethal: > 75 o F
Open Water
Prefer: Mid‐Water
Rarely: Near Bottom
Avoid: Shallow Shores
Where Do Cisco Live in Lakes?
Fall, Winter, and Spring
Oxygen High – Ideal
Cold – Ideal
Where Do Cisco Live in Lakes?
Early Summer
Oxygen High – Ideal
Epilimnion
Too Warm
Oxygen High – Ideal
Thermocline Cool ‐ OK
Oxygen Med – OK
Hypolimnion Cold ‐ Ideal
Where Do Cisco Live in Lakes?
Late Summer
Oxygen High – Ideal
Epilimnion
Too Warm
Oxygen Med – OK Thermocline Cool ‐ OK
Not Enough Oxygen
Hypolimnion Cold ‐ Ideal
Where Do Cisco Live in Lakes?
Late Summer – Hot Year
Oxygen High – Ideal
Epilimnion
Too Warm
Not Enough Oxygen
Thermocline Cool ‐ OK
Not Enough Oxygen
Hypolimnion Cold ‐ Ideal
SUMMER FISH KILL!
In What Types of Lakes Are Cisco Most Vulnerable?
Relatively Small and Shallow
Less Total Habitat; Oxygen on the Bottom Gone More Quickly
Longer Growing Season (i.e., further south, milder climate)
More Time to Use Up Oxygen on the Bottom
More Productive (i.e., more nutrients available)
More Decomposition; Oxygen on the Bottom Gone More Quickly
Future Climate Change – Some Relevant Predictions:
Winters will be warmer and shorter, Spring will come earlier and Fall later, Summer will be longer and hotter….
Longer Growing Season
More Time to Use Up Oxygen on the Bottom
Precipitation events will be more extreme,
Runoff will be greater,
More nutrients will reach lakes….
More Productive
Oxygen on the Bottom Gone More Quickly
Predicted Effects Climate Change on Cisco Occurrence
Number of Lakes with Cisco by Mid Century
200
180
160
140
120
100
80
175
128
60
88
40
53
20
0
Originally
Low Warming
Medium Warming
High Warming
Can We Prevent Disappearances?
Maybe….
Cisco Lake Vulnerability:
Relatively Small and Shallow Longer Growing Season
? More Productive ?
Climate Change Adaptation: Reduce Nutrient Inputs
Improve Watershed Land Use
Protect Natural Shorelines
Climate Change Adaptation: Triage – Protect the Resilient, Don’t Fight the Inevitable, Focus on the Restorable
Number of Lakes with Cisco by Mid Century
200
180
160
Restore!
140
120
Restore?
100
Don’t Fight
80
60
40
Protect
20
0
Originally
Low Warming
Medium Warming
High Warming
Summary and Conclusions
1) Cisco a keystone species, found in ~175 deep Wisconsin lakes
2) Cisco require cold water with oxygen; vulnerable to summerkills
3) Cisco threatened by climate warming; 30‐70% of lakes at risk
4) Some cisco lakes might be conserved if nutrient inputs reduced
Questions?